On a warm afternoon on Chicago's West Side, a young African-American man leans against the wall of the One Stop Food and Liquor store at the corner of Chicago Avenue and Homan Street. His puffy black jacket is so oversize that the collar hangs halfway down his back. Thirty feet up, a camera mounted on a telephone pole swivels toward him.

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Three miles away, in a bunkerlike, red granite building near Greektown, Ron Huberman watches the young man on a PC screen. "You see that guy?" asks Huberman, the 33-year-old chief of Chicago's Office of Emergency Management and Communications. "He's pitching dope - you can tell. Fucker."

The corner of Chicago and Homan used to be a haven for dealers slinging heroin and rock cocaine, the heart of a gangbanger free-fire zone. In 2003, the Windy City had 598 homicides, making it the country's murder capital.

"We've gotta figure out where's he keeping the goods," says Huberman, his voice breaking from a bout with the flu. "We're gonna go on the air" - call for a police car - "and bust him."

With a move of his mouse, Huberman pans to the right. We're looking down at a second man, in a beige coat. He has a brown paper bag in one hand and a wad of cash in the other. "He's involved," Huberman says, staring hard at the screen. No cop, even undercover, could ever get this close for this long. But the cameras - housed in checkerboard-patterned, 2-foot-tall boxes the police here call pods - can zoom in so tight I can see the wisps of a mustache. Huberman decides not to have his suspected dealers picked up; too much of an Enemy of the State move to pull with a reporter around, perhaps. But the footage will be stored for review by antinarcotics teams. "Now you see the power of what we're doing?" Huberman asks, still staring at the screen.

IT has been key to crime-fighting since patrol cars got radios in the 1920s. A couple of decades ago, London started installing surveillance cameras. In the 1990s, New York began crunching crime statistics and produced a near-miraculous improvement in public safety. By comparison, Chicago was a Cretaceous backwater.

But Chicago has evolved. A pilot network of 30 cameras keeps watch over the West Side, capturing images that have been used in more than 200 investigations. It's the first step on the way to a 2,250-camera system. And the electronic eyes are merely the most visible part of a strategy to completely remake police work in Chicago. A massive set of databases now collects and collates the minutiae of law enforcement - everything from mug shots to chains of evidence. Installed in patrol cars, it turns every PC in every station house into a node on a crime-fighting network. At headquarters, superintendents and commanders use it to pore over patterns of criminal behavior, figuring out how to deploy swarms of cops. Today, the murder rate is at its lowest point since the mid-'60s.

By embracing the cameras, the network, and this immensely powerful database, Chicago's once-creaky police force has become an inspiration for departments around the country looking to get spry. "There has never been another comprehensive program like this in a major police department," says Northwestern University political scientist Susan Hartnett, who's been studying the CPD for more than a decade. Whether it means the end of crime or the beginning of the surveillance state - or both - Chicago is building the future of law enforcement.

Officer Dave Dombkowski spent 13 years on the streets of Chicago before he went to work for Huberman. Today he's staring at the face of a thug on the screen of his gunmetal-gray laptop.

We're looking at a local street gang leader busted 16 times since 1996 - for heroin, DUIs, sex abuse, murder. We know all that because of a network of databases called Clear - Citizen Law Enforcement Analysis and Reporting. Clear lets Dombkowski tab through every mug shot, every alias, every scar. Give Clear a partial address, a nickname, a description of that tattoo on your perp's right arm, and it will track him down - even bring up his picture, for proof. The old databases would cough up information only if suspects gave their real names to the arresting officers, which happened about as often as the Cubs win the World Series. When Dombkowski was a patrol officer, he would trick people into the truth, telling them that the computer in his car was actually a new-jack polygraph, a "lie box" that could sort out fact from bullshit. But with Clear in his car, there's no more lying to Officer Dombkowski. No more tricks. "This is the real lie box," he says. "We can tell who you are."

Online rap sheets are really just a sliver of what Clear knows. In the station houses and at police headquarters, the database has become a kind of central nervous system for Chicago crime-fighters. It tracks all 466,000 pieces of CPD evidence, from recovered cigarette butts to confiscated drugs. But perhaps most important, it makes clear - and even predicts - patterns in the timing and geography of criminal behavior. That lets CPD chiefs know where to hang cameras. And it tells commanders like Jim Keating where to send troops.

A 25-year veteran - old-school enough to call police "coppers" - Keating heads up the department's Targeted Response Unit, a squad of 240 of Chicago's most amped-up officers assigned to the most crime-ridden neighborhoods of the city. It's not a stretch to call TRU the system's fist.

On his PC, Keating calls up Clear and shows me his hunting grounds. It's a map of the 25th District, near the city's northwest border. Every crime in the 25th from the past month is marked with an icon - black masks for robberies, orange bodies for homicides, blue guns for aggravated batteries with firearms. "Before, it would take six to eight months to develop a set of contacts in your district. And we had to rely on the detectives to put together the patterns," Keating says. "Now, it's click, click, click, and we have it all citywide." The 25th's map is dotted with a half-dozen blue guns, six black masks, and two orange corpses. Keating sends one of his guys to get me a Kevlar vest; we're going to the 25th tonight.